Summary:
As reported by an issue in github (https://github.com/facebook/Ax/issues/341)
This variable `no_max_parallelism` is not used by `choose_generation_strategy` but is still one of the functions input arguments.
Cleaning it up in this diff

Reviewed By: lena-kashtelyan

Differential Revision: D22576370

fbshipit-source-id: 13c3d41b2c66151508a8d5e1290ff73b0601010f